Distributed lighting systems typically have a central controller and have distributed/remote light fixtures connected to and controlled by the central controller, whereby the central controller receives power from a power source and receives control signals from one or more analog and/or digital control inputs, and, in turn, provides power and control signals to the light fixtures. For example, multiple Light Emitting Diode (LED) light fixtures, which typically use a very small amount of electrical power as compared to “standard” light fixtures that use incandescent or fluorescent lamps, can be connected to central controller by low voltage wiring which provides both power and control to the LED light fixtures.
The central controller may be connected to building power, which may comprise 120V/277V AC in the United States. With conventional lighting, if power to the building is interrupted, it is important to provide emergency lighting in a commercial or industrial space to enable the occupants to safely and quickly exit the building. Emergency power may be provided with a battery that is positioned in the light fixture itself, or may be provided by a backup generator that provides power in the event of a power interruption. In the case of LED lighting, the amount of electrical power that is consumed per light fixture is much lower than in conventional light fixtures, which opens up the possibility for different lighting schemes or configurations during a power interruption.
Additionally, unlike conventional lighting which are substantially controlled as a binary state (e.g., On/Off), LED light fixtures require enhanced control. For example, during a power outage, a conventional light fixture could simply be provided with power from an alternate source (i.e., a battery, a generator, etc.) whereas an LED light fixture not only needs power, but needs a control signal that will set the intensity of the light fixture and the color of the fixture.
However, in the event of a power interruption or failure, the central controller will cease functioning without power. Likewise, the various control inputs to the central controller will cease functioning without power. This means that even if power is provided to the central controller, the various peripheral devices will not be powered and therefore no control signals can be generated to send to the central controller.
So, while LED light fixtures provide some distinct advantages over conventional lighting, the control schemes are much more complicated and the ability to control LED lighting fixtures during a power interruption has been very limited.